1. Field of the Invention
The present invention relates to a photosensitive drum cleaning device used in an electrophotographic recording system.
2. Description of the Related Art
A prior electrophotographic recording system using magnetic toner employs a cleaning device for a photosensitive drum. This cleaning device serves to recover toner removed from the photosensitive drum, and is disclosed in a rotatable brush is employed for scraping residual toner off a photosensitive drum.
One prior device for recovering remaining toner removed from the surface of a photosensitive drum will hereinafter be described with reference to FIG. 1 of the accompanying drawings, FIG. 1 being a side elevational drawing illustrating one example of a prior cleaning device. As shown, a photosensitive drum 1 has a smooth surface and turns in the direction of the arrow. A toner image is formed via respective processes of charging, exposure, and development (not illustrated), and transferred onto paper by a transfer process. Denoted at 3a is residual toner not transferred onto the paper, but attached to the photosensitive drum 1. The residual toner 3a is wiped off the surface of the photosensitive drum 1 by a cleaning roll 4.
The cleaning roll 4 is made of a roll-shaped porous elastic material such as urethane sponge, etc. However, instead of this cleaning roll, a fur brush disclosed in U.S. Pat. No. 4,097,140 may also be used to achieve substantially the same effect.
The cleaning roll 4 for wiping off the residual toner 3a turns in the direction of the arrow A.sub.1, carrying scraped residual toner 3b to a sleeve 8 made of a non-magnetic material. The transferred toner 3b is forced to move onto the surface of the sleeve 8 under the magnetic force of a composite permanent magnet 7 whose S and N poles are alternately arranged, and carried toward a scraper 9 through the rotation of the sleeve 8 and the magnetic force of the permanent magnet 7. The scraper 9 is arranged to make contact with the surface of the sleeve 8 at one end thereof. Thus, the toner 3c as transferred is scraped off the surface of the sleeve 8 by the scraper 9. The scraper toner 3c moves along the surface of the scraper 9 and falls due to gravity and the magnetic force of the permanent magnet 7 turning in the direction of the arrow B, and is finally accumulated in a toner cartridge 11.
As soon as the toner 13 accumulated in the toner cartridge 11 reaches a prescribed amount, a detector means (not illustrated) detects it, informing the operator of the fact that the toner cartridge 11 should be replaced with a new one or the toner thrown away. The operator takes out the toner cartridge 11 from the cleaning device based on the information from the detector means for performing required processes. Moreover, there may be a case where the toner cartridge should be cleaned simultaneously with the supply of toner to a developing device, and when this happens it is again necessary to take out the toner cartridge 11 from the cleaning device.
However, with the cleaning device constructed as shown in FIG. 1, toner 3d is left behind on the scraper 9. The toner 3d at this time has remained on the scraper 9 due to a state of balance among gravity, magnetic force of the composite permanent magnet 7, and frictional force against the scraper 9. Thus, the toner 3d easily falls under a slight impact force when taking the toner cartridge 11 out of or into the cleaning device as described above.
Such a difficulty is found also in U.S. Pat. No. 4,097,140 or Japanese laid-open Patent Publication Nos. 64,274/80 and 132,372/81.
As described above, the recovered residual toner is accumulated on a portion corresponding to a toner cartridge guide as the recovered toner falls, and smears the interior of the cleaning device. Accordingly, the toner tends to smear the outer periphery of the toner cartridge and thus operator's hands, and further fall on other devices that will eventually be smeared. Another problem is that once the interior of the cleaning device is smeared, it was difficult to clean the interior of the cleaning device because of its small size, etc.